Nitrate flux in the Mississippi River: a big government problem
Mary Booth Environmental Working Group
Speaker Introduction by Professor Don Boesch integration
application
network
Nitrate flux in the Mississippi River: A Big Government Problem
Mary S. Booth Environmental Working Group Washington, DC April 13, 2006
Acknowledgements Sara Duke, Richard Bell, Richard Smith, Nancy Rabalais, Dave Wolock, Bob Larson, Tom Nolan, Bill Battaglin, Greg McIsaac, Thomas Jordan, Don Boesch and especially Richard Alexander
June 17 – July 18 bottom DO contours, 2004
http://www.ncddc.noaa.gov/ecosystems/hypoxia/data2004
Nutrient-laden sediment plume entering the Gulf of Mexico.
Photo by Nancy Rabalais
Size of hypoxic zone in July depends on flux of nitrate/nitrate in May Y (km2) = -1337953.4 + 672.1589 * Year + 0.0998* (May NO3+2 flux)
Turner, R. E., N. N. Rabalais, and D. Justic. 2006. Predicting summer hypoxia in the northern Gulf of Mexico: Riverine N,P, and Si loading. Marine Pollution Bulletin 52:139-148.
Gulf Hypoxia • Mississippi River/Gulf of Mexico Watershed Nutrient Task Force Hypoxia Assessment (Goolsby et al 1999, 2001) • Other models: SPARROW model (Smith et al 1997, Alexander et al 2000); McIsaac et al 2001; Donner et al 2003, 2004
The biggest source of nitrogen is non-point runoff from agricultural sources, especially inorganic fertilizers
Linking gulf hypoxia to farm practices It’s agreed that agricultural runoff is the the biggest source of nitrogen to the Gulf of Mexico… But what to do about it?
Fixing the Gulf: Mississippi River/Gulf of Mexico Watershed Nutrient Task Force Hypoxia Assessment and Action Plan Increased monitoring All voluntary compliance measures
Meanwhile…
Land use trends in the MRB hectares fertilized 88,000,000 86,000,000 84,000,000 82,000,000 80,000,000 78,000,000 76,000,000 74,000,000 1985
1990
1995
2000
Fertilizer N (kg)
2005
7,400,000,000 7,200,000,000 7,000,000,000 6,800,000,000 6,600,000,000 6,400,000,000 6,200,000,000 1985
hectares in conservation 15,000,000 10,000,000 5,000,000 0 1985
1990
1995
2000
2005
1990
1995
2000
2005
Current and proposed ethanol plant capacity in relation to corn acreage
No consistent change in extent of Dead Zone
http://www.gulfhypoxia.net/erf/Shelfwide%20Cruises.htm
What’s to be done?
No buffer
With buffer
Yearly agricultural payments in the MRB: Billions! $16,000,000,000 $14,000,000,000 $12,000,000,000 $10,000,000,000 $8,000,000,000 $6,000,000,000 $4,000,000,000 $2,000,000,000 $0
Commodity payments
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
Conservation subsidies
Objectives Characterize the current extent and location of agricultural N runoff in the MRB; Explore the relationship between agricultural subsidies and nitrate flux to the Gulf using actual and modeled data Where can increases in conservation payments be most effective?
Locations of large sites
Locations of “small-drainage” sites
Approach Regression model: time- and flow-weighted nitrate-N flux at USGS water quality monitoring sites as a function of: Runoff Fertilizer N inputs Population waste N inputs Animal waste N inputs Atmospheric nitrate deposition within each each site’s drainage for the years 1990-2002 (March – June)
Data sources Fertilizer inputs: USDA “planted acres” data, USDA fertilizer application rates; commercial fertilizer sales database Animal waste inputs: USDA Agricultural Census data, animal waste production estimates from various sources Human waste inputs: Census data on population; Resources for the Future and EPA databases on municipal N discharges Atmospheric nitrate deposition: National Atmospheric Deposition Program Runoff data: USGS database
Approach • Coefficients and exponents from the model applied to inputs data for each watershed in the MRB • Modeled watershed-level flux estimates multiplied by denitrification efficiency value from SPARROW model (Alexander et al 2000: in-stream denitrification losses are highest in small streams with a high sediment: water contact ratio and long travel time) • Modeled estimates summed to produce a whole-basin estimate for the MRB… • Hotspots of agricultural N flux evaluated in terms of subsidies
Checking the fertilizer estimates
Model structure flux_ha = average_runoff * ((lbfert_ha)2.13 + animN_ha + ndep_ha) + (popn_ha) flux_ha: kg NO3--N leaving the watershed, per ha/day average_runoff: daily runoff per hectare, in mm lbfert_ha: kg fertilizer nitrogen applied, per ha/year animN_ha: kg nitrogen as animal waste, per ha/year ndep_ha: kg NO3--N deposited per ha/year popn_ha: population* 0.0144 lb N per day/person
Results
Modeled flux compared to USGS flux: kg nitrate-N d-1 entering the Gulf
Spring nitrate loading model results compared to SPARROW model
SPARROW model and Spring Nitrate model comparison
SPARROW
Spring nitrate model
Nitrate flux vs. fertilizer inputs: big sites
Nitrate flux vs. fertilizer inputs: small sites
Proportion of land area accounting for spring flux
5% of area: 40% flux 10% of area: 65% flux 15% of area: 80% flux And 45% of crop subsidies
Commodity support dollars per hectare (County sum, 1995-2002)
< $150 $150- $400 $400 - $700 $700-$1500
Relationship between nitrate flux and corn subsidies
Value of fertilizer N lost in spring
• $270 million a year (average, 1990-2002) • At current fertilizer prices, $391 million
Critiquing the model: Is the nonlinear response of nitrate flux real, or an artifact of land drainage?
Percent of county drained, ~1978
0 – 10% drained 10 – 25% drained 25 – 45% drained >45% drained
Drainage map courtesy of Bill Battaglin, USGS
Percent of county fertilized
0 – 10% fertilized 10 – 25% fertilized 25 – 45% fertilized >45% fertilized
Percent of county drained, ~1978
0 – 10% drained 10 – 25% drained 25 – 45% drained >45% drained
Drainage map courtesy of Bill Battaglin, USGS
Percent of county fertilized
0 – 10% fertilized 10 – 25% fertilized 25 – 45% fertilized >45% fertilized
Nonlinearity of nitrate flux and inputs
Jordan, T. E., and D. E. Weller. 1996. Human contributions to terrestrial nitrogen flux. Bioscience 46:655-664.
Recommendations
Solutions to aquatic N loading depend on the nature of the problem Where fertilizer runoff is increased by artificial drainage, need wetland and riparian zone restoration Where runoff is a function of high N inputs, need reductions in inputs and diversification of land use
Whatever the nature of the problem… Conservation money needs to be increased in the Farm Bill. For Illinois, Indiana and Iowa: 2004 crop subsidies $2.7 billion 2004 Unfunded Applications for Environmental Quality Incentive Program (EQIP): $235 million in conservation and water quality grants 11,000 farmers 2004 Unfunded Applications for Wetlands Reserve Program (WRP): $411 million, 321,000 acres, 2,450 farmers
Commodity support dollars per hectare (County sum, 1995-2002)
< $150 $150- $400 $400 - $700 $700-$1500
Conservation payments per hectare (whole county basis, 1995-2002)
< $25 $25- $75 $75 - $150 150-$330
Estimates for restoration efforts
Mitsch, W. J., J. W. J. Day, J. W. Gilliam, P. M. Groffman, D. L. Hey, G. W. Randall, and N. Wang. 2001. Reducing nitrogen loading to the Gulf of Mexico from the Mississippi River Basin: strategies to counter a persistent ecological problem. Bioscience 51:373-388.
Current relationship of conservation area to fertilized area for watersheds of the MRB
Proposed relationship between conservation area and fertilized area
A legislative goal: Conservation compliance! Farmers should not expect to receive federal commodity support dollars unless they demonstrate responsible use of inputs and compliance with conservation goals
www.ewg.org
Question Time
Mary S. Booth Environmental Working Group Washington, DC April 13, 2006
Question Time (cont’d)
Mary S. Booth Environmental Working Group Washington, DC April 13, 2006
